INCREASE IN MUCOSAL AND CONNECTIVE TISSUE-TYPE MAST-CELLS IN THE STOMACH WITH ACETIC ACID-INDUCED ULCER IN RAT

Gastric ulcers were induced in rats by acetic acid treatment, and the mast cell kinetics in the lesions were studied. Within 24 h, mast cell s had disappeared from the treated site and from the marginal zone, co rresponding to the area of severe tissue injury. Regenerating epitheli um appeared at day 10, and the lesion had healed by day 30. In this he aling process, the number of mast cells was significantly increased, a nd their density in the regenerating mucosa, marginal mucosa, and marg inal muscularis propria was 3.2 1.8, and 7.5-fold the control level, r espectively. The increase in the number of mast cells was preceded by an increase in the percentage of S-phase mast cells. Mast cells in the mucosa were Alcian blue (AB)(+)/safranin (S)(-) and rat mast cell pro tease (RMCP) I-/II+, consistent with the features of mucosal mast cell s throughout the observation period. On the other hand, most mast cell s in the muscularis propria exhibited AB(+)/S+ and RMCP I+/II+ in the early period of ulcer healing. The latter feature was changed to RMCP I+/II- on day 30, indicating that immature CTMC appeared and then deve loped into mature CTMC during the ulcer healing. The significant chang e in the number of mast cells suggests that mast cells play an importa nt role in the development and healing of gastric ulcers.